Re: MPLS EIGRP backdoor links - SoO

Since Paul has already mentioned that you can verify the SoO value
with "show ip eigrp topology XXXX", I would like to throw in some
additional info here. I`ve built a mini lab because I wanted to know
in detail how EIGRP carries the SoO value across the backdoor link.

After capturing some packets[1] on the backdoor link I could find out
that EIGRP is using the TLV type 260 for SoO. The data inside the TLV
looks something like this.

01 04 -> TLV Type (260)
00 14 -> TLV Length: 20 bytes
0a 00 19 00 -> TLV references IP routing TLV with route 10.0.25.0
00 00 00 -> Not sure yet?
08 -> Ext Community Lengh? 8 bytes
00 03 -> Ext Community Type?
00 64 00 00 00 02 -> SOO Ext communit value: 100:2

I haven't figured out all the header fields yet, but I could at least
identify the SoO value of 100:2 in the last 6 bytes of the TLV. The
hex data is from packet 38 in the capture file[1]. Wireshark/Scapy
doesn't decode the TLV at the moment, but I promise to write a patch
as soon as I've identified all the header fields correctly ;-)

Petr Lapukhov has also written a great document about EIGRP SoO:
http://blog.ine.com/2010/04/29/understanding-eigrp-soo-and-bgp-cost-community/

Best regards,

Jochen

1) http://www.cloudshark.org/captures/327a223fadf3

On Tue, Nov 1, 2011 at 8:14 PM, Tom Kacprzynski <tom.kac_at_gmail.com> wrote:
> Hello,
> I'm working on a lab using EIGRP as the protocol for MPLS VPN. This
> scenario has a backdoor link. I'm testing the Site of Origin feature, but
> can't seem to find any way to check the actual SoO on the CE router using
> EIGRP commands. Does anyone know how/if I could do that?
>
> I can see it in BGP table but how do I see it in EIGRP
>
> Rack1R6#sh ip bgp vpnv4 rd 100:1 155.1.67.0/24
> BGP routing table entry for 100:1:155.1.67.0/24, version 338
> Paths: (1 available, best #1, table VPN-A)
> Advertised to update-groups:
> 1
> Local
> 0.0.0.0 from 0.0.0.0 (150.1.6.6)
> Origin incomplete, metric 0, localpref 100, weight 32768, valid,
> sourced, best
> Extended Community: SoO:100:60 RT:100:1
> Cost:pre-bestpath:128:28160 <----------------------
> 0x8800:32768:0 0x8801:10:2560 0x8802:65280:25600 0x8803:65281:1500
> mpls labels in/out 22/nolabel(VPN-A)
>
>
>
> Thank you,
>
> Tom
>
>
> Blogs and organic groups at http://www.ccie.net
>
> _______________________________________________________________________
> Subscription information may be found at:
> http://www.groupstudy.com/list/CCIELab.html

Blogs and organic groups at http://www.ccie.net
Received on Wed Nov 02 2011 - 01:11:15 ART